28978640 has 20 divisors (see below), whose sum is σ = 67375524. Its totient is φ = 11591424.

The previous prime is 28978637. The next prime is 28978657. The reversal of 28978640 is 4687982.

It can be written as a sum of positive squares in 2 ways, for example, as 12559936 + 16418704 = 3544^2 + 4052^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a junction number, because it is equal to n+sod(n) for n = 28978591 and 28978600.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 181037 + ... + 181196.

Almost surely, 2^28978640 is an apocalyptic number.

28978640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

28978640 is an abundant number, since it is smaller than the sum of its proper divisors (38396884).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

28978640 is a wasteful number, since it uses less digits than its factorization.

28978640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 362246 (or 362240 counting only the distinct ones).

The product of its (nonzero) digits is 193536, while the sum is 44.

The square root of 28978640 is about 5383.1812156011. The cubic root of 28978640 is about 307.1562333663.

The spelling of 28978640 in words is "twenty-eight million, nine hundred seventy-eight thousand, six hundred forty".